1. Field of the Invention
The present invention relates to an apparatus for carrying substrates, and more particularly to a cassette device for carrying a number of substrates in fabricating liquid crystal display panels.
2. Description of Related Art
In the present flat panel display (such as liquid crystal display) fabs, to facilitate the transfer or storage of the panels and prevent the substrate from being contaminated, it is common to insert the panels into a cassette having slots arranged in order. Hence, the panels are transported to the next processing step. Alternatively, the panels in bulk are transferred to a predetermined position of an apparatus during a processing step by means of a robot arm equipped with the apparatus, wherein the panels are picked up by the robot arm and transferred to a processing chamber of the apparatus. In some cases, the cassette carrying the panels in bulk is transferred to the processing chamber of the apparatus so that the panels in bulk are processed simultaneously.
FIG. 6 shows the currently available cassette, wherein a cassette 600 is generally assembled with screws 610. A large number of screws 610 need to be used in this case, hence, the assembly is time-consuming and causes difficulty in maintenance. For example, bottom supporting rails 620 are securely engaged with end plates 630 by means of the screws. The screws tend to become loose after the cassette has been used for a long time, resulting in substrates 640 in bulk falling from the cassette and breaking. On the other hand, the slots of partition plates 650 are below the end of wires of transistors at the periphery of the substrates 640, hence, the wires are susceptible to being scratched during loading/unloading of the panels, bringing expense through waste panels. Furthermore, in the known cassette 600 where the substrates 640 are loaded, the substrates 640 project out of the cassette 600 without any protection. Hence, the substrates 640 are susceptible to hitting against an outside object and breaking. Further, due to the projection of the panels, the cassettes cannot be stacked. Thus, an excessive area of a clean room is occupied by the cassettes in stock. Further, drain holes at the bottom of the cassette are poorly designed, and thus, water is accumulated after cleaning process. Accordingly, it is difficult to keep the cassette dry.
Therefore, it is desirable to provide a substrate carrying devise to mitigate and/or obviate the aforementioned problems.